Cassette seal

Abstract

A cassette seal comprising an inner ring and an outer ring has angle or L-shaped profiles which are arranged together inside each other to form a substantially rectangularly bounded hollow space. The inner ring has a rubber coating (6) for support and sealing on an axle or shaft. The leg of one ring which extends in the radial direction and is facing away from the sealed-off medium has a sealing lip formed from an elastomer material which extends into the hollow space and rests against the leg of the other ring extending in the axial direction. The sealing lip is followed by at least one dust lip spaced at an axial distance away from the sealed-off medium. The leg of the other ring which is facing the sealed-off medium and which extends in the radial direction is sealed against the leg of the one ring extending in the axial direction by a labyrinth gap (12). The contact surface assigned to the dust lip changes into the contact surface assigned to the sealing lip without enlargement of the diameter.

What is claimed is: 
     
       1. A cassette seal for a shaft comprising an inner ring having a substantially L-shaped profile and an outer ring having a substantially L-shaped profile wherein said inner ring is arranged within said outer ring with said L-shaped profiles having an opposed orientation thereby forming an essentially rectangularly bound hollow space; said inner ring L-shape profile having a first leg extending substantially parallel to the axial direction of said ring with said first leg having an inner surface for facing said shaft;   an elastomer coating adhered to the inner surface of said inner ring first leg for contacting said shaft to provide sealing and support;   said inner ring L-shaped profile having a second leg extending in the radial direction outward from said inner ring first leg;   said outer ring L-shaped profile having a first leg extending substantially parallel to said axial direction;   said outer ring L-shaped profile having a second leg extending in the radial direction inward from said outer ring first leg; wherein,   the second leg of one of said rings, which will be remote from a sealed-off medium has mounted thereon a member fabricated from an elastomer material with said elastomer member extending into said hollow space and having formed thereon a sealing lip and at least one dust lip;   said sealing lip is positioned within said hollow space and rests against the first leg of said other ring;   said dust lip is spaced from said sealing lip at an axial distance in the direction toward said second leg of said one ring;   the second leg of said other ring which will be adjacent said sealed-off medium is arranged with respect to the first leg of said one ring to form a labyrinth gap for providing restricted fluid communication between said sealed off medium and said hollow space;   means for providing at least one choke point located within said labyrinth gap thereby providing a pumping effect between said sealed-off medium and said hollow space; and   said elastomer member is formed such that the contact surface of said dust lip changes into the contact surface of said sealing lip without enlargement of the diameter.   
     
     
       2. A cassette seal according to claim 1 wherein said member having said sealing lip formed thereon is mounted on the second leg of said inner ring for sealing a housing rotating about a stationary axis. 
     
     
       3. A cassette seal according to claim 1 wherein said member having said sealing lip formed thereon is mounted on the second leg of said outer ring for sealing a rotating shaft. 
     
     
       4. A cassette seal according to claim 1, 2 or 3 wherein said labyrinth gap is formed by a slot located in said first leg of said one ring engaged by said second leg of said other ring. 
     
     
       5. A cassette seal according to claim 4 wherein said slot is formed by a U-shaped projection at the end of said first leg of said one ring wherein the end of said second leg of said other ring is received by said U-shaped projection. 
     
     
       6. A cassette seal as recited in claim 1, 2 or 3 wherein the contact surface of said dust lip changes with reduced diameter into the contact surface of the sealing lip. 
     
     
       7. A cassette seal as recited in claim 6 wherein the contact surface of the dust lip and the sealed-off shaft enclose an acute angle. 
     
     
       8. A cassette seal as recited in claim 7 wherein the acute angle is about 30° to 60°. 
     
     
       9. A cassette seal according to claim 1, 2 or 3 wherein at least two dust lips are provided.